IR spectroscopy measurements may be useful for a variety of purposes including aerospace, automotive and industrial applications, as well as biological and bio-medical applications. For example, infrared (IR) radiation is readily absorbed by materials in association with relative motions (vibrations) of atoms such as carbon, hydrogen, oxygen and nitrogen. As such, IR spectroscopy measurements may indicate a condition of a wide variety of organic as well as inorganic materials.
For example, organic polymer materials including resin-fiber composite materials may degrade over time due to a variety of reasons including ultraviolet (UV) light exposure. Chemical degradation to a polymer structure may occur, thereby affecting the desired properties of the polymer structure including structural integrity such as strength of a composite material or adhesion of an organic surface coating on said composite material.
Chemical degradation of a polymer material may be caused by exposure to normal environmental sources of UV such as sunlight as well as exposure to artificial sources of UV such as metal halide light sources and other indoor light sources. Exposure of organic materials to UV radiation may result in the breaking of existing polymer chemical bonds and/or the formation of new polymer chemical bonds. Maintenance of organic containing materials subjected to UV light exposure requires a determination of the degree of UV-induced physical and/or chemical degradation of the organic containing material, including polymer composite materials or coatings thereon.
For example, polymer composite materials such as fiber-resin materials including carbon reinforced fiber have been used as structural materials, for example in portions of an aircraft. Preparation and use of such polymer composite materials may further include the use of surface treating polymers such as epoxies. The exposure of polymer composite materials to UV energy may result in the degradation of desirable properties of such materials including strength and adhesion properties to other materials, such as overlying coatings of material, including paint. Although the exposure to such material to UV light may result in visual indications of UV damages including gradations of discoloration, such visual indications of damaged or compromised composite material are subjective and not sufficiently reliable or quantifiable to assess a degree of degradation and a level of required maintenance. For example, UV exposure is mitigated or repaired with hand wiping using an 80% acetone and 20% water solution until the surface damage is removed. To the Inventor's knowledge, no adequate non-destructive method exists in the prior art to determine when the mitigation is sufficient or if more mitigation is needed to insure good paint adhesion to a repaired surface.
One non-destructive method of ascertaining the condition of a polymer composite material, such as the degree of heat damage to composite materials includes IR spectroscopy of the composite material as outlined in U.S. Pat. No. 7,115,869, which is hereby incorporated by reference in its entirety.
Other non-destructive methods in the prior art include using IR spectroscopy to determine the amount of a chromated conversion coating on a metallic substrate (U.S. Pat. No. 6,794,651), determining the amount of an anodize coating on a metallic substrate, (U.S. Pat. No. 6,784,431), determining an amount of opaque coating on a substrate (U.S. Pat. No. 6,903,339), and determining an amount of heat exposure to a resin-fiber composite substrate (U.S. Pat. No. 7,115,869), all of which are fully incorporated by reference herein.
None of the above methods and associated devices, however, disclose a method or device that is suitable for performing IR spectroscopy to quantify a level of UV energy induced damage to an organic material containing surface, and to thereby determine a degree of damage present in the organic material containing surface, particularly in a field environment, such as in aircraft maintenance.
Thus, there is a continuing need for improved IR non-destructive testing methods including a method that is suitable for performing IR spectroscopy to quantify a level of UV energy induced damage in organic material containing surface, such as a surface of a polymer composite material, and to thereby determine a degree of damage present in the organic material containing surface, particularly in a field environment, such as in aircraft manufacture and maintenance.
Therefore it is an object of the invention to provide a method that is suitable for performing IR spectroscopy to quantify a level of UV energy induced damage in an organic material containing surface, such as a surface of a polymer composite material, and to thereby determine a degree of damage present in the organic material containing surface, particularly in a field environment, such as in aircraft manufacture and maintenance.